Rate limiting

Rate limiting is a strategy to limit network traffic. As the name suggests, it puts a limit on how often someone can repeat an action (such as trying to log into an account) within a given time period. Rate limiting can help mitigate certain types of malicious activity such as brute force attacks. It is also useful to reduce the load on your mail server.

Concurrency

To limit the number of concurrent IMAP and POP3 connections that a user can have, use the imap.rate-limit.concurrent setting. For example:

[imap.rate-limit]
concurrent = 4

Requests

To limit the number of IMAP and POP3 requests that a user can make within a given time period, use the imap.rate-limit.requests setting. For example:

[imap.rate-limit]
requests = "2000/1m"